1. Field of the Invention
The present invention concerns a surface coil arrangement for a magnetic resonance tomography of the type wherein an arrangement of coil elements is mounted on an antenna, and wherein the antenna can be extended in size by at least one further antenna element that likewise carries an arrangement of at least one coil element.
2. Description of the Prior Art
A surface coil arrangement of the above general type is known from PCT Application WO 03/025607 A1.
Such surface coil arrangements are used in magnetic resonance tomography (MRT), as reception coil systems and possibly at the same time as transmission coils, for which purpose they are placed directly at the region to be examined on the body surface of a patient examined in the MR tomography apparatus. The examination subject is thereby exposed essentially from only one side, i.e., signals are acquired only on one side. In order to counteract the decay of the signal intensity that occurs with increasing distance from the reception coil, arrangements known as “array coils” are used, meaning an arrangement of a number of reception coils. A number of reception coils are operated simultaneously in such an arrangement. The signals of the individual coils (array channels) are supplied to separate receivers and an image is initially calculated for each array channel. These images are then added using suitable combination logarithms, and an image with a large measurement field and a high signal/noise ratio is created. These array coils are suite, for example, for spinal column examinations in which the spinal column can be completely mapped without coil exchange or coil displacement. Coils known as body coils that are situated very close to the body and are used in abdomen or back imaging are a further application.
Conventional body array coils are known that are designed for placement on an average patient body. MR acquisitions in a plane perpendicular to the body axis of the patient depend essentially on the “patient body circumference”. This varies from patient to patient, for example as a result of obesity, pregnancy or even because the patient is an infant.
If the patient is obese or if the patient is a pregnant woman, the sides of the patient are not covered by the body array. This leads to a signal discontinuity in the middle of the body of the patient. By contrast, if the patient is extremely thin or a child, the coil is too large for the patient. The coil edges rest on the examination table; the coil cannot be optimally fixed.
WO 03/025607 A1 describes a surface coil arrangement of a gradient system for MR tomography in which a number of coil elements are arranged next to one another. The coil elements are attached to one another without overlap by latches or snaps or the like. A step-by-step adaptation to the circumference of the measurement region to be examined can thereby ensue. Nevertheless, due to fit inaccuracies poorly-exposed areas or poorly-received signals still can occur when the coil arrangement is not situated entirely surrounding the body of the person to be examined because it is too large or does not fully cover the body region because it is too small.
EP 1 521 094 A1 describes a similar arrangement in which a large number of coil elements are mechanically connected with one another, arranged in columns and rows.
DE 102 44 173 describes with an antenna arrangement for magnetic resonance apparatuses in which an inductive coupling of adjacent antenna groups is effected. If the patient is obese or if the patient is a pregnant woman, the sides of the patient are not covered by the body array. A signal discontinuity in the middle of the body of the patient thus occurs.